Traditionally, an electrical connector is assembled by inserting a contact into a contact receiving opening provided in a housing. When the contact is incorrectly or inversely inserted into the housing, particularly in the case of a substantially square contact, failure of engagement of the electrical connector with a mating connector is likely to occur. In order to prevent incorrect insertion, the contact and/or the housing have been formed with irregularities that only allow the contact to be inserted into the housing in the correct direction.
For example, Japanese Patent Publication No. 10-144379 teaches a housing having a step disposed on an inner wall of a contact receiving opening and a contact with a projection that abuts the step when it is inversely inserted into the housing. In addition, Japanese Patent Publication No. 2004-103349 teaches a connector having a housing with a projection provided in the contact receiving opening and a contact with a recess that avoids abutting the projection when correctly inserted in the contact receiving opening. The electrical connector also includes a stabilizer, which has been conventionally used to prevent incorrect insertion of the contact.
The recent trend toward smaller more high density electrical connectors requires that smaller contacts be developed having dimensions smaller than a diameter of a wire connected to the contact. The contact is configured to have a diameter as wide as the diameter of the wire at an end closest to a contact insertion end and a smaller diameter at an end opposite from the contact insertion end.
Because the contact insertion end must be large enough to accommodate the larger end of the contact, it is difficult to provide irregularities on the contact and the housing adjacent to the contact insertion end to prevent incorrect insertion of the contact. For example, since a gap will exist between the contact and the housing, a projection on the contact can easily advance into the housing without having to align with a recess in the housing, thus allowing incorrect insertion.
In order to solve this problem, it has been proposed that a front edge of the projection of the contact be engaged with a recess of the housing in order to further prevent incorrect insertion. However, the front edge of a small projection may easily scrape by an inner wall of the housing, allowing incorrect insertion. Further, even when the contact is inserted correctly, it is difficult to have the contact smoothly transition between the differently dimensioned areas within the housing. This is especially difficult when the electrical connector is connected to a wire having a cross section of about 0.22 to 0.5 mm.